1. Field of the Invention
This invention relates to lockable closure fastenings for apertures, especially the access mouths of containers or other enclosures.
2. Description of the Prior Art
The term `closure` employed herein embraces any form of cover, cap or lid, spanning and at least partially closing the spatial extent of an aperture.
Some means is usually provided for locating and securing or fastening the closure in place upon the aperture.
Thus closures commonly employ a threaded fastening for fitting to a container, with complementary threads on the closure and a peripheral rim profile, typically upon an upstanding neck, of the container mouth or aperture.
In such threaded closure fastenings one aspect of the invention is particularly concerned with a closure fastener thread-locking device.
This effectively also becomes a fastener-locking element--and in particular a self-locking (threaded) closure fastening.
The term `thread` employed herein embraces any form of cooperative, interactive mating or interlocking arrangement, whether of multiple complementary members or otherwise.
In the threaded fastener art generally, when a plurality of members are threaded together, it is advantageous in some uses to provide a means for `locking` or jamming the threads and thereby inhibiting further relative movement of these threaded members--in either an unlocking (and unfastening) or a locking (and fastening) direction.
Moreover, if such a thread-locking element is automatically effected after a certain relative thread travel, a more secure thread fastening and thus convenient overall installation is achieved.
It is known to employ an intermediate resiliently deformable (temporary) binding agent for such a locking purpose--for example a synthetic plastics material bonding to a metal thread.
Once locked, unlocking generally either requires excess physical force to `over-ride` the mechanical lock, typically breaking or rupturing the locking material, or severing and prising or tearing away the locking material from the thread body.
Other aspects of the invention are concerned with the integration of a closure locking device with a seal.
The term `seal` employed herein embraces any form of mechanically close, tight or interference fit, relative disposition of elements, whether a fluid (i.e. gas or liquid)-tight, or hermetic seal, or otherwise.
Alternatively, the seal may be operative only in a `security` sense--i.e. as an element that must be deliberately and visibly broken to gain admission to the contents of an article sealed thereby.
Thus, in some instances, the elements for, and associated implementation of, closing, fastening, locking and sealing may be integrated `seamlessly`.
Container closures commonly provide some form of seal, in order to secure the container contents, and inhibit the egress (i.e. leakage or spillage) of contents from the container--or indeed the ingress of contaminants into the container.
Such sealing has hitherto commonly relied upon an internal resilient annular washer incorporated in the base of a closure cap, and compressed by contact with the upper rim of a container neck once the cap is securely fastened in place.
This very compression at the last stage of fastening may act as a fastening lock, particularly when vacuum or relatively low internal container pressures are imposed.
The resilience, (and in particular the characteristic `spring click` noise exhibited when depressed and released) of such caps under a sealed container pressure differential has been relied upon in the past as an indicator that the container seal has not been broken. Unfortunately, this differential pressure and associated pressure signal can be re-created by miscreant interference--and so is not a reliable guide.
Sealing may thus represent a critical factor in the container closure--to the extent that some positive indication should be furnished, if the seal has not been positioned, is not yet completely effective, or less been subsequently displaced or otherwise interfered with.
Hence the convenient and apposite nomenclature `tamper-evident closure` is used for such locking seals--that is seals which resist tampering, but if overcome, provide a positive indication thereof.
In that regard, the term `tamper-proof` is less apposite, since a humanly-devised security system inevitably admits of human ingenuity in overcoming the security hurdle presented.
The storage of foodstuffs in containers represents an important use of such tamper evident closures.
In such uses, the aforesaid integration of threaded fastener locking and seal formation--such that a container closure is automatically secured and locked into position on a container as a seal is formed--is particularly advantageous.
With such integration, unlocking (i.e. for subsequent unfastening and opening) of the closure requires breaking of the seal--desirably as a deliberate and, most importantly, self-evident, preliminary step.
In the closure sealing art it is known to employ a peripheral sealing band, typically of synthetic plastics material, temperature shrunk into place after fitment of the closure.
However this form of seal is vulnerable to removal, simply by applying an elevated temperature (for example by immersion in hot water) and reinstatement by reverse cooling--allowing intervening tampering with the contents.
Indeed malicious tampering with container contents, with attendant commercial and consumer health risks, has become more prevalent--making the provision of a tamper-evident (container) closure highly desirable--even virtually essential in such applications as baby food storage, in order to maintain consumer confidence in the edibility of the product.
For such applications it will be appreciated that the integrated self-locking fastening and sealing of a container closure is particularly advantageous.
According to one aspect of the invention there is provided a closure for an aperture with a co-operative peripheral or boundary (rim) profile, such as the mouth of a container, the closure incorporating a self-locking fastener (element) which cooperates with the peripheral (rim) profile and securely locks the closure on to the aperture upon limiting engagement thereof.
Desirably, the fastener locking element is integrated with a peripheral security seal, disposed to inhibit unlocking, unfastening and opening of the closure once installed.
While such a seal may be over-ridden or broken, in order to overcome the inhibition upon closure unfastening and opening, the very act of seal breakage provides permanent and vital evidence--even on casual inspection--that the closure has been tampered with.
Randomly generated, matched pairs of easily visible security markings on the seal and closure respectively could be provided in production, after initial closure fastening and seal installation, in order to prevent substitution of another (fresh) seal after the initial container opening.
A multiple `combination` rotating drum indentation mechanism, applied in rolling contact with the periphery of the container closure, could provide such security marking as a post-production step upon closure fastening.
According to another aspect of the invention there is provided a lockable threaded container closure fastening utilising complementary threads upon the container mouth and closure, with a (thread) locking element disposed to selectively either run aligned therebetween, allowing relative rotation thereof, for fastening and unfastening of the closure, or to become misaligned therewith (for example, axially offset therefrom), to obstruct such rotation.
With such arrangements, although the closure is re-usable--i.e. it may be (securely) fastened and unfastened repeatedly--once the initial (integrated) lock and seal has been (visibly) broken by the first act of opening, the automatic or self-locking and sealing element is operative only once.
A container must also be able to withstand vertical stacking loads, such as are encountered in transit and point-of-sale display, without damage to, or reduction in the efficacy of, the individual (internal) closure seal.
For example, if a container lid deforms or buckles at its center, the load on a peripheral rim seal could be eased. Alternatively, if the seal itself bears the load, it may be crushed--to the detriment of the intimacy of its sealing contact with the closure and container.
Some aspects of the present invention provide just this facility, by accommodating and distributing such loads through the threaded fastener locking element--optionally in conjunction with a travel limit and locking abutments on the rim of the container neck.
Although the invention has particular application to the closure, and in particular container closure art, some other aspect admit of a broader use--for example in the (self-locking threaded) fastener art generally.
In that art it is known to employ bonded intermediate thread locking elements of synthetic plastics material, for example Nylon (Trade Mark), as a resiliently deformable bridge between the metal threads of a nut and bolt.
This thread lock may inhibit thread slackening under vibration or may maintain a predetermined locking torque initially applied.
However, such locking elements are re-usable without any visible evidence that the initial lock has been broken--which undermines their original purpose.
Similarly, in the wider container closure art it is known for example to apply, by moulding in situ a plastics closure, with a break-off locking collar, to a metal can with a threaded neck, but this is not suitable for container contents unable to be brought close to the necessary elevated closure-forming temperatures after processing.
Thus, in some of its embodiments, the invention provides a closure for tamper-proofing containers, such as jars, bottles, cans or other enclosures, which have apertures bounded by externally threaded neck-rings, onto which closures with complementary threads can be securely (rotatably) fastened, or `screwed` to close and seal the apertures.
Such embodiments provide a means of ensuring that, once a container has been closed and sealed by such a closure, it cannot be unsealed and opened--and consequently that the contents cannot be tampered with--without there being visible evidence that the seal has been disturbed, and the closure opened or vulnerable to tampering.
A conventional threaded closure for fastening onto an externally threaded container neck-ring commonly has a top panel and a dependent skirt.
In the case of a metal closure, it is known for the skirt to be rolled inwardly or outwardly at its lower edge, to form a circumferential bead, and either the bead or the skirt is deformed, to enable the closure to engage the threads on a neck-ring, for fastening into sealing engagement with the sealing surface of a neck-ring.
In the case of a plastic closure, the skirt normally terminates in a moulded thread, which likewise engages the threads on a neck-ring, so that the closure can be fastened into sealing engagement therewith.
Unfortunately, such conventional metal or plastic closures can be removed and re-applied without there being any visible evidence that this has been done.
Consequently the fact that a container appears outwardly to be securely sealed with such a conventional closure is no guarantee that the contents have not been tampered with.